I believe one of us has mixed up the order of operations. In your final step you have rec2020toxyzd50=np.matmul(M,d65tod50) , so you seem to do \mathbf{M} \cdot \mathbf{M_A} while I effectively do the reverse, \mathbf{M_A} \cdot \mathbf{M}. Since matrix multiplication doesn’t commute, we get different results.
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